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dkim: Implement internal dkim signing and verification
This patch implements internal DKIM signing and verification.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,260 @@ | ||
| package main | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "context" | ||
| "crypto" | ||
| "crypto/ed25519" | ||
| "crypto/rand" | ||
| "crypto/rsa" | ||
| "crypto/x509" | ||
| "encoding/base64" | ||
| "encoding/pem" | ||
| "fmt" | ||
| "io" | ||
| "net/mail" | ||
| "os" | ||
| "path" | ||
| "path/filepath" | ||
| "strings" | ||
| "time" | ||
|
|
||
| "blitiri.com.ar/go/chasquid/internal/dkim" | ||
| "blitiri.com.ar/go/chasquid/internal/envelope" | ||
| "blitiri.com.ar/go/chasquid/internal/normalize" | ||
| ) | ||
|
|
||
| func dkimSign() { | ||
| domain := args["$2"] | ||
| selector := args["$3"] | ||
| keyPath := args["$4"] | ||
|
|
||
| msg, err := io.ReadAll(os.Stdin) | ||
| if err != nil { | ||
| Fatalf("%v", err) | ||
| } | ||
| msg = normalize.ToCRLF(msg) | ||
|
|
||
| if domain == "" { | ||
| domain = getDomainFromMsg(msg) | ||
| } | ||
| if selector == "" { | ||
| selector = findSelectorForDomain(domain) | ||
| } | ||
| if keyPath == "" { | ||
| keyPath = keyPathFor(domain, selector) | ||
| } | ||
|
|
||
| signer := &dkim.Signer{ | ||
| Domain: domain, | ||
| Selector: selector, | ||
| Signer: loadPrivateKey(keyPath), | ||
| } | ||
|
|
||
| ctx := context.Background() | ||
| if _, verbose := args["-v"]; verbose { | ||
| ctx = dkim.WithTraceFunc(ctx, | ||
| func(format string, args ...interface{}) { | ||
| fmt.Fprintf(os.Stderr, format+"\n", args...) | ||
| }) | ||
| } | ||
|
|
||
| header, err := signer.Sign(ctx, string(msg)) | ||
| if err != nil { | ||
| Fatalf("Error signing message: %v", err) | ||
| } | ||
| fmt.Printf("DKIM-Signature: %s\r\n", | ||
| strings.ReplaceAll(header, "\r\n", "\r\n\t")) | ||
| } | ||
|
|
||
| func dkimVerify() { | ||
| msg, err := io.ReadAll(os.Stdin) | ||
| if err != nil { | ||
| Fatalf("%v", err) | ||
| } | ||
| msg = normalize.ToCRLF(msg) | ||
|
|
||
| ctx := context.Background() | ||
| if _, verbose := args["-v"]; verbose { | ||
| ctx = dkim.WithTraceFunc(ctx, | ||
| func(format string, args ...interface{}) { | ||
| fmt.Fprintf(os.Stderr, format+"\n", args...) | ||
| }) | ||
| } | ||
|
|
||
| results, err := dkim.VerifyMessage(ctx, string(msg)) | ||
| if err != nil { | ||
| Fatalf("Error verifying message: %v", err) | ||
| } | ||
|
|
||
| hostname, _ := os.Hostname() | ||
| ar := "Authentication-Results: " + hostname + "\r\n\t" | ||
| ar += strings.ReplaceAll( | ||
| results.AuthenticationResults(), "\r\n", "\r\n\t") | ||
|
|
||
| fmt.Println(ar) | ||
| } | ||
|
|
||
| func dkimDNS() { | ||
| domain := args["$2"] | ||
| selector := args["$3"] | ||
| keyPath := args["$4"] | ||
|
|
||
| if domain == "" { | ||
| Fatalf("Error: missing domain parameter") | ||
| } | ||
| if selector == "" { | ||
| selector = findSelectorForDomain(domain) | ||
| } | ||
| if keyPath == "" { | ||
| keyPath = keyPathFor(domain, selector) | ||
| } | ||
|
|
||
| fmt.Println(dnsRecordFor(domain, selector, loadPrivateKey(keyPath))) | ||
| } | ||
|
|
||
| func dnsRecordFor(domain, selector string, private crypto.Signer) string { | ||
| public := private.Public() | ||
|
|
||
| var err error | ||
| algoStr := "" | ||
| pubBytes := []byte{} | ||
| switch private.(type) { | ||
| case *rsa.PrivateKey: | ||
| algoStr = "rsa" | ||
| pubBytes, err = x509.MarshalPKIXPublicKey(public) | ||
| case ed25519.PrivateKey: | ||
| algoStr = "ed25519" | ||
| pubBytes = public.(ed25519.PublicKey) | ||
| } | ||
|
|
||
| if err != nil { | ||
| Fatalf("Error marshaling public key: %v", err) | ||
| } | ||
|
|
||
| return fmt.Sprintf( | ||
| "%s._domainkey.%s\tTXT\t\"v=DKIM1; k=%s; p=%s\"", | ||
| selector, domain, | ||
| algoStr, base64.StdEncoding.EncodeToString(pubBytes)) | ||
| } | ||
|
|
||
| func dkimKeygen() { | ||
| domain := args["$2"] | ||
| selector := args["$3"] | ||
| keyPath := args["$4"] | ||
| algo := args["--algo"] | ||
|
|
||
| if domain == "" { | ||
| Fatalf("Error: missing domain parameter") | ||
| } | ||
| if selector == "" { | ||
| selector = time.Now().UTC().Format("20060102") | ||
| } | ||
| if keyPath == "" { | ||
| keyPath = keyPathFor(domain, selector) | ||
| } | ||
|
|
||
| if _, err := os.Stat(keyPath); !os.IsNotExist(err) { | ||
| Fatalf("Error: key already exists at %q", keyPath) | ||
| } | ||
|
|
||
| var private crypto.Signer | ||
| var err error | ||
| switch algo { | ||
| case "", "rsa3072": | ||
| private, err = rsa.GenerateKey(rand.Reader, 3072) | ||
| case "rsa4096": | ||
| private, err = rsa.GenerateKey(rand.Reader, 4096) | ||
| case "ed25519": | ||
| _, private, err = ed25519.GenerateKey(rand.Reader) | ||
| default: | ||
| Fatalf("Error: unsupported algorithm %q", algo) | ||
| } | ||
|
|
||
| if err != nil { | ||
| Fatalf("Error generating key: %v", err) | ||
| } | ||
|
|
||
| privB, err := x509.MarshalPKCS8PrivateKey(private) | ||
| if err != nil { | ||
| Fatalf("Error marshaling private key: %v", err) | ||
| } | ||
|
|
||
| f, err := os.OpenFile(keyPath, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0660) | ||
| if err != nil { | ||
| Fatalf("Error creating key file %q: %v", keyPath, err) | ||
| } | ||
|
|
||
| block := &pem.Block{ | ||
| Type: "PRIVATE KEY", | ||
| Bytes: privB, | ||
| } | ||
| if err := pem.Encode(f, block); err != nil { | ||
| Fatalf("Error PEM-encoding key: %v", err) | ||
| } | ||
| f.Close() | ||
|
|
||
| fmt.Printf("Key written to %q\n\n", keyPath) | ||
|
|
||
| fmt.Println(dnsRecordFor(domain, selector, private)) | ||
| } | ||
|
|
||
| func keyPathFor(domain, selector string) string { | ||
| return path.Clean(fmt.Sprintf("%s/domains/%s/dkim:%s.pem", | ||
| configDir, domain, selector)) | ||
| } | ||
|
|
||
| func getDomainFromMsg(msg []byte) string { | ||
| m, err := mail.ReadMessage(bytes.NewReader(msg)) | ||
| if err != nil { | ||
| Fatalf("Error parsing message: %v", err) | ||
| } | ||
|
|
||
| addr, err := mail.ParseAddress(m.Header.Get("From")) | ||
| if err != nil { | ||
| Fatalf("Error parsing From: header: %v", err) | ||
| } | ||
|
|
||
| return envelope.DomainOf(addr.Address) | ||
| } | ||
|
|
||
| func findSelectorForDomain(domain string) string { | ||
| glob := path.Clean(configDir + "/domains/" + domain + "/dkim:*.pem") | ||
| ms, err := filepath.Glob(glob) | ||
| if err != nil { | ||
| Fatalf("Error finding DKIM keys: %v", err) | ||
| } | ||
| for _, m := range ms { | ||
| base := filepath.Base(m) | ||
| selector := strings.TrimPrefix(base, "dkim:") | ||
| selector = strings.TrimSuffix(selector, ".pem") | ||
| return selector | ||
| } | ||
|
|
||
| Fatalf("No DKIM keys found in %q", glob) | ||
| return "" | ||
| } | ||
|
|
||
| func loadPrivateKey(path string) crypto.Signer { | ||
| key, err := os.ReadFile(path) | ||
| if err != nil { | ||
| Fatalf("Error reading private key from %q: %v", path, err) | ||
| } | ||
|
|
||
| block, _ := pem.Decode(key) | ||
| if block == nil { | ||
| Fatalf("Error decoding PEM block") | ||
| } | ||
|
|
||
| switch strings.ToUpper(block.Type) { | ||
| case "PRIVATE KEY": | ||
| k, err := x509.ParsePKCS8PrivateKey(block.Bytes) | ||
| if err != nil { | ||
| Fatalf("Error parsing private key: %v", err) | ||
| } | ||
| return k.(crypto.Signer) | ||
| default: | ||
| Fatalf("Unsupported key type: %s", block.Type) | ||
| return nil | ||
| } | ||
| } |
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